Method of making contact members for crossbar switch



Oct. 27, 1964 A. w. VINCENT METHOD OF MAKING CONTACT MEMBERS FORCRQSSBAR SWITCH 2 Sheets-Sheet 1 Filed July 18, 1960 INVENTOR.

ANDREW W. VINCENT FIG. 3

A iorndj Oct. 27, 1964 A. w. VINCENT 3,153,840

METHOD OF MAKING CONTACT MEMBERS FOR CROSSBAR SWITCH Filed July 18, 19602 Sheets-Sheet 2 F I 7 IN VEN TOR.

ANDREW W. VINCENT United States The present invention relates to a crossbar switch for connecting various electric conducting members to eachother in various possible combinations, and more particularly to animproved method of forming contact members of a cross bar switch.

This application is a continuation-in-part of my US. patent applicationSerial No. 645,609, filed March 12, 1957, now Patent No. 2,950,350,granted August 23, 1960.

One object of the present invention is to provide an improved method ofmaking the contact members of the channel strip, or link bar, or crossconductor, of a cross bar switch.

Another object of this invention is to provide a method for makingimproved contact members for the channel strip, or link bar, or crossconductor, of a cross bar switch.

Still another object of the invention is to provide improved channelstrip, link bar or cross conductor construction for a cross bar switch.

Other objects of this invention will be apparent hereinafter from thespecification, the accompanying drawings, and the appended claims.

In the drawings:

FIG. 1 is a fragmentary perspective view of a cross-bar switch havingcontact members made in accordance with on embodiment of this invention;

FIG. 2 is a fragmentary perspective view of a portion of a channel stripor link bar or cross conductor of this switch having contact membersconstructed in accordance with and by one embodiment of this invention;

FIG. 3 is a perspective view of a portion of the line strip or lineconductor of the cross bar switch;

FIG. 4 is a perspective view of a modified cross conductor, channelstrip, or link bar, made according to this invention;

FIG. 5 is a plan View on an enlarged scale, illustrating one stage inthe manufacture of a channel strip, link bar, or cross conductoraccording to this invention;

FIG. 6 is a section on the line 6--6 of FIG. 5, looking in the directionof the arrows;

FIG. 7 is a cross section on the line 77 of FIG. 5 looking in thedirection of the arrows; and

FIG. 8 is a fragmentary sectional view illustrating another step in themanufacture of the channel strip, link bar, or cross conductor.

The type of cross-bar switch, to which the present invention is applied,is disclosed in my United States Patents No. 2,731,516, granted January17, 1956, and No. 2,729,- 706, granted January 3, 1956, and in mypending U.S. ap plication Serial No. 645,609 above referred to, andreference may be had to those patents and application for a moredetailed disclosure of this general type of switch. Suffice it to saythat a cross bar switch has a desired number of line conductors arrangedin banks extending parallel to each other, and any desired number ofcross conductors, or link bars, which alternate with the line conductorsand cross these at right angles. These cross conductors or link bars arein the form of channel strips. Electrical contacts are made at selectedpoints where the link bars cross the line conductors, by moving selectedportions of the line conductors, as by pushers that move at right anglesto bothe the line conductors and the link bars, to bring the selectedportions of the line conductors into electrical contact with the linkbars.

The type of switch to which the invention relates is atent ice showngenerally in FIG. 1. This switch comprises a plurality of line plates 31which extend from front to rear approximately in vertical planesarranged parallel to and spaced laterally from each other. These lineplates 31 have suitable stiffening flanges 33 extending laterally attheir top edges, and similar stiffening flanges (not shown) at theirbottom edges. The line plates 31 are fastened at front and rear to frontand rear frame members, of which one is shown fragmentarily at 25.

In addition to the physical connection of the front frame bars with therear frame members by means of the line plates 31, the front and rearframe members are also connected to each other by a flange plate 41which is shown only fragmentarily and which extends from front to rearalong the right hand edge of the structure near the top thereof. Thisplate serves as a support for magnets which operate the selector orinterposer mechanism of the switch.

Each line plate 31 is provided with a number of openings or windows inthe form of wide vertical slots 61, the number of such slots being equalto the number of banks of cross-conductors which are to be employed. Onone side of each line plate 31 (the far side when viewed in FIG. 1),there is fastened a plate 63 of insulating material, which serves toclose the windows 61 except for apertures 65 formed in the insulatingplate 63, which apertures are equal in number to the number of crossconductors or link bars mounted on the line plate 31. These aperturesreceive and tightly hold the cross conductors, or link bars, or channelstrips 67 which extend through these apertures approximatelyperpendicular to the line plates 31.

Line conductors, which are adapted to electrically connect with thecontact portions of the link bars 67, extend longitudinally along theline plates 31, at elevations slightly above the respective link bars67. Each line conductor comprises a continuous strip 71 (FIG. 3) ofthin, flexible, resilient metal, suitably connected to a stationaryterminal at its front end and to a similar terminal at its rear end. Thefastening of the ends of each line conductor 71 to the stationaryterminals serves to anchor each line conductor against longitudinalmovement and to hold the ends thereof in a given horizontal plate justabove the top of the link bar 67 with which the line conductor isintended to cooperate.

At various intervals throughout its length (corresponding to theintervals at which the banks of crossing link bars are spaced from eachother) each line conductor 71 is provided with a flexible, resilient arm73 (FIGS. 1 and 3) that extends first laterally relative to the lengthof the main strip 71 and then a substantial distance in a generaldirection parallel to the main strip 71. Each arm 73 has a wider freeend 75 formed with a slight upward tilt relative to the arm 73, fromwhich a reversely projecting finger 77 extends. There is one of thesearms 73 for each of the link bars 67 with which the line conductor 71 isto make selective contact.

On the face of each line plate 31 opposite from the insulating plate 63(that is on the near face when viewed in FIG. 1) the line plate 31 isprovided in each space between two successive windows or slots 61, witha metal plate 31, which has parts near its top for supporting andguiding the selector mechanism and the contact closing mechanism, asfurther described below. Each line plate also has a lateral projection83 near its top, and a similar lateral projection (not shown) near itsbottom, on each of which there is fastened a leaf spring 85 of resilientmetal, which is longitudinally slotted to receive in the slot thereof, apusher 37 formed of stifi insulating material. in FIG. 1, only one ofthe springs 85 is shown for clearness in illustration. Each pusher has ahook 89 extending over the free end of the spring 85, and a similar hook(not shown) extending over the free end of the similar spring at thebottom of the structure. By means of these hooks tend to raise eachpusher to its uppermost position, but

the pusher is capable of limited vertical downward movement, flexing thesprings. Since the springs are flexible vertically but not horizontally,they serve not only as supports but also as guides accurately holdingthe pushers 87 in alignment and preventing lateral, displacement Ithereof. 7

Each pusher 87 extends vertically through the slots 91 (FIG. 3) betweenthe main spring arms 73 and the fingers 77 of vertically aligned lineconductors, whereby the line conductors are guided against shiftinglaterally out of proper alignment. Each pusher '87, has, at an elevationjust above each of the line conductors 71 associated therewith, aprojecting lug 93 (FIG. 1) having a downwardly faced foot 95.

The underside of each portion 75 of the line strip or .line conductor isprovided with a contact member 101 firmly secured, as by welding, to'themember 75 and extending in a general direction crosswise of theconductor 71 and crosswise of the line plate 31 on which this condoctoris mounted. Each of the contact members 101'is adapted to cooperate witha pair of contact members 1433 and 105 suitably secured, as by welding,to the top surfaces ofa pair of spring tongues 197 and 109 (FIGS. 1, 2and 3) formed on a link bar 67. When a portion 75 of a finger 73 isslightly depressed (by downward movement of a pusher 87) from its normalelevation, the flat bottom face of the contact member 101 of that finger'73 comes down against the flat top surfaces of and makes electricalcontact with the two contact members 103 standing guide tongues 145, 147which engage opposite sides ofthe bar. These are formed on the plates81, so that each bar 143 is guided at a number of different points alongits length.

At its front end (the left end as viewed in FIG. 1), each actuator bar143 has a small opening 151 in which is received the laterally-extendingend of finger 153 of an upstanding leaf spring member 155 that issecured to the associated line plate 31 near the front end thereof. Thisspring tends to draw the 'bar 143 resiliently forwardly, and holds therear end of the bar constantly in firm engagement with the magnet lever131. A stationary car 161, which extends laterally from an upstandingrigid post 163, engages in the opening 141 at the rear of each actuatorbar 143, and serves with the spring finger 153 to hold each acuator barat the desired elevation.

The horizontal motion of an actuator bar 143 is transmitted into avertical motion of the associated pushers 87 through a rocker comprisinga slotted main or bottom flange 181, and two integral upstandingportions 185 and 187. Each rocker is hingedly connected to a stationarylug 171 by a hinge including spring member 197 as more particularlydescribed in my application Serial No. 645,- 609 above-mentioned. Thepusher springs 85 exert upward force tending to move the free end of theflange 181 of therocker upwardly to an extent limited by contact of thisend with a fixed stop 2197 formed as an integral laterally bent lug onthe plate 81. The same extensions 89 on the pushers 87, which form thehooks engaging over the springs 85, have their top surfaces engagedagainst the under faces of the free ends of the rocker flanges 181 r sothat the fixed stop 207 determines not only the upper position of therocker flange 181 but also the upper position of the pusher 87, and anydownward swinging move ment of the rocker flange 181 will cause downwardcorthe switch structure, near the top thereof, are a number of selectorwires or rods 231 equal in number to the num ber of vertical stacks orbanks of link bars, one selector wire or rod 231 being for use with eachindividual stack or cross conductor.

At its left end each selector wire 231is anchored to a cross tensionspring (not shown) which in turn is an chored to a stationary part ofthe frame. The opposite or right hand end of each selector wire 231 isconnected to a selector magnet (not shown), There is a selector magnetassociated with each selector wire 231; and when any one of the selectormagnets is energized, it will operate to pull the selector wire 231connected with that magnet against the resistance of the cross tensionspring which is associated with the selector wire.

Mounted on each selector wire are several interposer assemblies, one foreach line plate 31. Thus, if the switch structure includes ten lineplates, there will be ten interposer assemblies on each of the severalselector wires 231.

Each selector wire 231 is guided in a horizontal slot 261 (FIG. 1)formed in the upper portion of each plate 81 and opening at its forwardend at the top edge of the plate 81. A little to the left of each plate81 and its associated actuating bar 143, in the space between this barand the next adjacent actuating bar of the next adjacent line plate 31,there is an actuator assembly comprising a coil spring 265 and aninterposer, one part of which is denoted at 279 in FIG. 1. Eachinterposer is frictionally connected to the associated coil spring 265which is necked down for this purpose, A portion of the interposerextends through a guide slot or pocket formed in the clip 211 which issecured to the associated rocker 185, 187 and has a portion which isengaged against the left side of the associated actuating bar 143 whenthe interposer is moved rightwardly into operative position.

The bottom edge of each actuating bar 143 has a notch 391 in it in thevicinity of each rocker. The forward end 303 of each notch constitutesthe abutment surface, or

force-transmitting part of the actuating bar, for moving the selectedrocker upon longitudinal. movement of the V actuating bar.

When one of the selector magnets is energized to draw its selector wirerightwardly, all the interposers mounted on this selector wire are movedrightwardly so that the effective part'of the interposer is broughtbetween the part 211 of the rocker and the abutment surface 303 of theactuating bar 143. This effective, or. force-transmitting part of theinterposer almost fills the space between the parts 211 and 303 when theactuating bar 143 is in its relaxed or forward position. Therefore, if,while the interposer is held in effective position, the actuating bar143 is moved rearward by energization of its actuating magnet, theshoulder 303 of the actuating bar will push rearwardly against theinterposer, transmitting force through the interposer and swinging theassociated rocker on its hinge, thus depressing the rear end of therocker flange 181 to cause downward movement of a pusher 87 to close thevertical stack or bank of switches at this particular crossing point bybringing the contacts 101 of the line conductors 71 of the stack intoengagement with g the contacts 103, 105 of the crossing link bars 67.

When a particular vertical stack or bank of line conductors 71, mountedon one of the line plates 31, isto be electrically connected to aparticular vertical stack or bank of link bars 67, the selector magnetfor this particular bank of link bars is first energized to actuate theindividual selector wire 231 relating to this particular bank of linkbars. All of the interposers 279 mounted on this actuated wire 231 willthus be moved into effective position; A brief instant after theselector magnet is energized, the particular actuating magnet for theparticular line plate 31 in question will be energized, thereby causingrearward longitudinal movement of the actuator bar of this particularline plate 31. This will rock the rocker 181, 185, which is located atthe crossing of the particular selector wire 231 and the particularactuator bar 143, thereby depressing the pusher 87 of this particularcrossing, and connecting all of the line conductors 71 of thisparticular line plate 31 with the respective link bars 67 of theselected bank of link bars. But the other rockers on the same line plate31 will not be actuated because the interposers 279 for these otherrockers have not been shifted to operative position. Other rockers onother line plates 31 will not be moved regardless of whether or not theinterposers have been moved to effective position, because the actuatingbars 143 of these other line plates will not be moved. The actuating bar1 33, which has been moved to operative position, will be maintained inoperative position to hold the contacts closed, as long as its actuatingmagnet remains energized, even though the magnet that moves the selectorwire 231 is deenergized. As long as the actuating magnet remainsenergized, there can be no further actuation of any of the switches ofthis particular line plate 31. However, the switches on any other lineplate 31 are available for actuation, either in connection with the samebank of link bars or in connection with another bank of link bars.

The above construction is illustrated and described in full detail in mycopending application Serial No. 645,- 609, above mentioned. The presentapplication relates specifically to the structure of the link bars andto a method of manufacturing the link bars.

Each link bar 67 is formed with a plurality of pairs of flexible tongues1G7 and 109 that are spaced from one another longitudinally of the linkbar. The contacts 193 and 105 are carried by these tongues. The linkbars are of inverted channel shape; and the tongues 197 and 199 areintegral with the tops of the inverted channel bars. Each channel bar 67itself is made of beryllium copper. In a first punching operation, theside edges of the tongues 167 and 109 are sheared from the tops of aninverted channel 67, and the two tongues 167 and 109 together (not yetcut apart) are arched upwardly out of the plane of the base flange,leaving a bridging portion 108 which integrally connects the two tongues107 and 109 together. In this same stamping operation, the bridgingportion 138 is preferably cut adjacent its sides partly away from thetongues 167 and 199 and bent down to form the two tangs 111. Then thechannel 67 is heat treated to harden the metal to the desired degree.For example, the channel may be heated to approximately 700 F. and heldat this temperature for approximately one hour, or may be heated toapproximately 600 F. and held at this temperature for approximately twohours. After heating the channel is allowed to cool slowly in air toroom temperature. Any known form of heat treatment of beryllium coppermay be employed, either in addition to, or as a substitute for thespecific treatment mentioned above as an example, the point of thisphase of the invention being that this heat treatment (whatever itsexact nature) of beryllium copper, which both hardens and stressrelieves at the same time, takes place while the two tongues 157 and 169are still integrally connected endwise to each other by the bridge 198to form parts of a single curved member or arch which at both ends isintegral with the main flange or top of the inverted channel member.

This arched formation of the tongues and bridge is inherently stable, sothat these parts maintain, during heat treatment, the correct shape towhich they were formed during the first punching operation. Experienceshows that if the two tongues were cut apart before the heat treatment,so that each was supported only in cantilever fashion, there is greatlikelihood of warping or dis tortion during the heat treatment, unlessthe tongues are held in place by jigs or fixtures. Any such distortionis extremely undesirable in electrical switch parts such as these, wherethe parts must be held to close tolerances, to permit the relativelymovable members to make proper contact with each other despite theslight movement which is desirable when the switch is to be closed, andto prevent false closing or false contact when the switch is intended tobe open. The integral arch formation, during the heat treating step,holds the spring fingers in the desired position, without the need ofjigs.

Vhen the heat treatment, which relieves the stresses set up in the metalduring the punching and forming step, is finished, the channel 67 issubjected to a second punching operation, to separate the two tongues107 and 109 from each other at the center of the arch by cutting out thebridge portion 198 so that the two tongues can move up and down indepe.dently without rubbing endwise on each other. This step is accomplishedaccording to this invention by using a pair of punches 113 and 114 whichhave active faces consisting of an inclined portion and a plane tipportion. The inclined portions 116 and 118 of the two punches areparallel and complementary to each other; and the plane tip portions 121and 122 of the two punches are parallel and formed at right angles tothe direction of operating movement of the two punches. The punches aredisposed so that their plane portions 121 and 122, respectively, engage,on their punching strokes, the tongues 1197 and 199, respectively,adjacent the bridging portion 1418 connecting the tongues. On thepunching strokes, then, the inclined surfaces 116 and 118 of the twopunches twist and break out the bridge portion 1&8 from the tongues 197and 1119, thereby separating the tongues. The cuts, which are made whenthe tabs 11 are formed, define breaking lines so that when the bridgeportion 1118 is twisted, it will break away cleanly from the tongues 167and 1119. The partial shearing of the metal provides a notch effectwhere the tabs join the tongues at the inner ends of the tabs, and actsas would a scored line, predisposing the metal to break straight acrossthe ends of the bridge portion 1%.

As soon as the bridging part 198 is twisted out from between a pair oftongues 1G7, 109, through their resiliency the tongues will spring backto position to be at the same height and inclination which they hadbefore severance of the bridge from the tongues. Thus they will occupythe same positions which they occupied upon completion of theheat-treatment.

After heat treatment and preferably after severance from one another ofthe tongues of a link bar, the contact members 163, 1135 are brazed onthe adjacent ends of each pair of tongues. The contact members 1133,1125 are preferably made of gold, although palladium may be used also.Either metal gives long life to the make-and-break contacts involved.

The contact members 1113 and 195 are elongated in the directiontransverse to the length of the channels 67 and parallel to the lengthof the adjacent line plate 31 and line conductor 71. Thus, these twocontact members lie at right angles to the length of the contact member191 on the line conductor.

When a portion 75 of a line conductor is at its normal elevation, thecontact member 101 of that portion 75 is spaced slightly above thenormal elevation of the cooperating contact members 103 and 195, so thatthe switch at this point is open. When a portion 75 of a line conductoris slightly depressed (by downward movement of the insulating pusher 37)the contact member 191 of that portion 75 is brought down firmly againstthe top surface of both of the cooperating contacts 1433 and on the linkbar s7, firm electric contact with both of them, and thus closing theswitch at this point to connect the line conductors 71 electrically withthe link bar 67. The use of the two contact members 163 and 195, mountedfor independent resilient movement on proper operation.

'their respective tongues 197 and 10?, makesthe switch silver alloy orberyllium copper (preferably the latter).

The contact members 101 of the line conductors may be made of gold or ofpalladium or of any other metal.

In prior cross bar switches, it has been customary to make the contactmembers of palladium backed up by a cheaper metal such as a piece ofnickel silver, the nickel silver constituting, with the palladium, abi-metallic strip welded as a unit to the conductor, this bi-metallicstrip being necessary in the prior construction in order to secureenough height to insure good contact and It will be noted that in FIG. 1of my Patent 2,729,706 that the contact-carrying tongues of the link barare flat tongues lying in the same plane as the top of the invertedchannel bar and that the same construction is present in my prior Patent2,731,516 as shown in FIG. 5 thereof. Because of this construction, thecontact members 90! and 11d of Patent Nos. 2,729,706 and 2,731,516,respectively, had to be built up to a substantial height to insuresatisfactory contact.

In the construction of the present application, however, the contactmembers 103 and 1435 are carried by spring tongues 107 and 109 whichthemselves incline upwardly from the plane of the normal top surface ofthe link bars 67, so it is no longer necessary to make the contactmembers themselves so thick. The ability to use thinner contact membersof gold or palladium only, instead of thicker members of palladiumbacked up by nickel silver alloy, makes for a material saving in costs.

For an individual lead-out arrangement, channel bars 367 (FIG. 4) may beused corresponding in general to short sections of the channel bars '57.Each channel bar 367 has a pair of spring fingers'1tl7, 109 identicalwith those previously described and having contact pieces 1G3,

' 105 thereon, such as previously described. 'Each section 367 is.connected to a conductor leading to an individual terminal. At one endeach depending flange of each channel member 367 has a small ear 375 bywhich it may connected to the conductor.

While the invention has been described in connection with a specificembodiment thereof, it will be understood that it is' capable of furthermodification, and this application is intended to cover any variations,uses, or adaptations of the invention following, in general, theprinciples of the invention and including such departures from thepresent dsclosure as come within known or customary practice in the artto which the invention pertains and as may be applied to the essentialfeatures hereinbefore set forth, and as fall within the scope of theinvention-or the limits of the appended claims.

Having thus described my'invention, what I claim is:

1. The method of forming an electric switch contact member having a pairof resilient aligned tongues, which comprises the steps of subjecting astrip of beryllium copper having and approximately plane portion, fromwhich the tongue are to be formed, to a punching operation to sever theside edges of the tongues from the rest of the strip and to arch the twotongues together out of the plane of the strip without completelysevering the adjacent ends of the two tongues from each other, heattreating the strip to relieve stresses therein and to harden the stripwhile the tongues remain arched and integrally connected to each otherso that'the arched condition of the connected tongues will tend tomaintain them in intended position without warpage during heattreatment, and then severing the adjacent ends of the two tongues fromeach other after the conclusion of the heat treatment. 7 p

2. The method as defined in claim 1, further including the step ofsecuring electric contact portions of gold to the tongues after theconclusion of heat treatment'and after the two tongues are severed fromeach other.

3. The method of forming an electric switch contact member having a pairof resilient aligned tongues, which punching operation to sever the sideedges of the tongues from the rest of the strip and to arch the twotongues together out of the plane of the strip while partially severingthe adjacent ends of the two tongues from each other, heat treating thestrip to relieve stresses therein and to harden the strip While thetongues remain arched and integrally connected to each other so that thearched condition of the connected tongues will tend to maintain them inintended position without warpage during heat treatment, and then, afterthe conclusion of the heat treatment, completing severing of theadjacent edges of the two tongues from each other.

4. The method of forming an electric switch contact member having a pairof resilient aligned tongues, which comprises the steps of subjecting astrip of beryllium copper having an approximately plane portion fromwhich the tongues are to be formed to a punching operation to sever theside edges of the tongues, to arch the two tongues together out of theplane of the strip,

. and to partially sever the adjacent ends of the tongues from eachother while leaving a bridge of metal narrower than the width of saidadjacent ends of the tongues integrally connecting the tongues together,heat treating the strip to relieve stresses therein and to harden thestrip while the tongues remain arched and integrally connected to eachother so that the arched condition of the connected tongues will tend tomaintain them in intended position without warpage during heattreatment,

and then, after conclusion of the heat treatment, subjecta ing thebridge to a twisting operation to sever the bridge from the adjacentends of the tongues and to sever the two tongues from each other.

5. The method as defined in claim 4, wherein the steps of heat treatingthe strip compn'ses heating it to approximately 700 F. and holding it atsaid temperature for approximately one hour and then allowing it to coolslowly.

- 6. The method as defined in claim 4 wherein the heat treating stepcomprises heating the strip to 600 F. and then holding it at thattemperature for approximately two hours and then allowing it to coolslowly.

7. The method of forming an electric switch contact member, whichcomprises subjecting a strip of metal to a punching operation to stampup and partially sever from said strip an elongated arched portionconnected at its opposite remote ends to the strip, stress-relieving andhardening the strip while said portion remains arched j and integrallyconnected at both ends to the strip, and then cutting the arched portiontransversely midway of its length to form two resilient tongues whoseadjacent ends face toward each other and lie in the same plane.

S. The method of forming an electric switch contact member according toclaim 7, further including the step of securing two electric contactportions of a different metal from the metal of said strip at oppositesides of the longitudinal center of the strip after the conclusion ofstress-relieving and hardening and after cutting the arched portion, thecontact portions being secured, respectively,.to the two tongues formedby the cutting operation. a

9. The method of forming an electric switch contact 7 member, whichcomprises subjecting a strip of metal to a punchingop eration to stampup and partially. sever from said strip an elongated arched portionwhich is connected at its distal ends to the strip, and which is ofgradually decreasing width from each of said ends toward the center ofthe arched portion, and partially severing the central portion of saidarched portion from the remainder of said arched portion along parallellines extending part-way from opposite lateral sides of the archedportion inwardly, thereby to leave a short-length narrow bridge portionat the center of the arched portion, heat-treating the strip while saidarched portion remains arched and integrally connected at its distalends to the strip, and then severing the bridge portion from the archedportion to form two resilient tongues whose adjacent ends face towardeach other.

10. The method of forming an electric switch contact member according toclaim 9, further including the step of securing two electric contactportions of a different metal from the metal of said strip at oppositesides of said bridge portion after the conclusion of the heat treatmentand after severing the bridge portion, the contact portions being soseparated from one another that, after severing of the bridge portion,the contact portions are secured to adjacent ends of the two tonguesformed.

11. The method of forming an electric switch as claimed in claim 9,wherein the bridge portion is severed from the rest of the archedportion by a twisting operation effected by moving two punch toolstoward each other from above and below the arched portion, respectively,to move the part of the arched portion which is at one side of saidbridge portion downwardly while moving the part of the arched portionwhich is at the other side of said arched portion upwardly to twist thebridge portion loose from said two parts of the arched portion.

References Cited in the file of this patent UNITED STATES PATENTS1,309,354 Dallmeyer et a1. July 8, 1919 2,135,417 Tinnerman Nov. 1, 19382,169,056 Place Aug. 8, 1939 2,486,285 Hurst Oct. 25, 1949 2,614,195Kitto Oct. 14, 1952 2,729,706 Vincent Jan. 3, 1956 2,731,516 VincentJan. 17, 1956 2,740,735 Swain Apr. 3, 1956 2,750,463 Roeser June 12,1956 2,789,899 Donachie Apr. 23, 1957 2,802,082 Kalwo Aug. 6, 1957

7. THE METHOD OF FORMING AN ELECTRIC SWITCH CONTACT MEMBER, WHICHCOMPRISES SUBJECTING A STRIP OF METAL TO A PUNCHING OPERATION TO STAMPUP AND PARTIALLY SEVER FROM SAID STRIP AN ELONGATED ARCHED PORTIONCONNECTED AT ITS OPPOSITE REMOTE ENDS TO THE STRIP, STRESS-RELIEVING ANDHARDENING THE STRIP WHILE SAID PORTION REMAINS ARCHED AND INTEGRALLYCONNECTED AT BOTH ENDS TO THE STRIP, AND THEN CUTTING THE ARCHED PORTIONTRANSVERSELY MIDWAY OF ITS LENGTH TO FORM TWO RESILIENT TONGUES WHOSEADJACENT ENDS FACE TOWARD EACH OTHER AND LIE IN THE SAME PLANE.